This invention relates to prints or drawings that give an illusion of depth, often referred to as three dimensional or 3-D pictures. This invention particularly relates to anaglyphs that yield a 3-D image when viewed through appropriately colored lenses.
An anaglyph is a picture generally consisting of two distinctly colored, and preferably, complementary colored, prints or drwaings. The complementary colors conventionally chosen for commercial printings of comic books and the like appears to be orange and green-blue. Each of the complementary colored prints contains all elements of the picture. For example, if the picture consists of a car on a highway, then the anaglyph will be imprinted with an orange car and highway, and with a green-blue car and highway. For reasons explained below, some or all of the orange colored elements of the picture are horizontally shifted in varying amounts in the printing process relative to their corresponding green-blue elements.
The anaglyph is viewed through glasses having lenses tinted about the same colors as the anaglyph (hereinafter, "3-D glasses"). While orange and green-blue lenses are optimally used with an orange and green-blue anaglyph, red and blue lenses work satisfactorily in practice and apparently are conventionally used.
The orange elements in the picture are only seen through the blue lens, the red lens "washing out" the orange elements. For the same reason, the green-blue elements are only seen through the red lens. Hence, each eye sees only one of the two colored pictures. But because the different colored elements are horizontally shifted in varying amounts, the viewer's eyes must turn inward to properly view some elements, and turn outward to properly view others. Those elements for which the eyes turn inward, which is what the viewer does to observe a close object, are naturally perceived as close to the viewer. Elements for which the viewer's eyes turn outward are correspondingly perceived as distant. Specifically, if the blue lens covers the viewer's right eye, which generally is the present convention, then any green-blue element shifted to the left of its corresponding orange element appears to the viewer as distant or far away. The element appears more distant the greater the leftward shift. Conversely, as a green-blue element is shifted only slightly leftward, not at all, or even to the right of its corresponding red element, that element will appear increasingly closer to the viewer.
In addition to horizontally shifting the element pairs relative to each other, some users of anaglyphy for comic books also vertically shift the element pairs a slight amount relative to each other. Those users believe that the slight vertical shift improves the 3-D effect.